The present invention relates generally to electrical components, methods for making electrical components and machines employing such electrical components. In particular, it relates to multifunctional electrical components with both electrical and mechanical structural functionality and in particular is directed to the use of such components in automatic reproducing machines such as office copiers, duplicators and printers. More specifically, the component comprises an electrically insulating polymer matrix which is filled with an electrically insulating fibrous filler capable of heat conversion to an electrically conducting fibrous filler where at least one continuous electrically conductive path is formed by the in situ heat conversion of the electrically insulating fibrous filler.
In electrostatographic reproducing apparatus commonly used today a photoconductive insulating member is typically charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member which corresponds to the image contained within the original document. Alternatively, a light beam may be modulated and used to selectively discharge portions of the charged photoconductive surface to record the desired information therein. Typically, such a system employs a laser beam. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developer powder referred to in the art as toner. Most development systems employ developer which comprises both charged carrier particles and charged toner particles which triboelectrically adhere to the carrier particles. During development the toner particles are attracted from the carrier particles by the charged pattern of the image areas of the photoconductive insulating area to form a powder image on the photoconductive area. This toner image may be subsequently transferred to a support surface such as copy paper to which it may be permanently affixed by heating or by the application of pressure.
In commercial applications of such products it is necessary to distribute power and/or logic signals to various sites within the machine. Traditionally, this has taken the form of utilizing conventional wires and wiring harnesses in each machine to distribute power and logic signals to the various functional elements in an automated machine. While the conventional approach has been immensely effective in providing convenience products, with increasing demands on manufacturing cost and the desire for automated assembly, different approaches have to be provided. For example, since individual wires and wiring harnesses are inherently very flexible, they do not lend themselves to automated assembly such as with the use of robotics. Furthermore, such harnesses may have to be handled or moved several times to make all connections required. This is a highly labor intensive exercise frequently requiring routing of the several harnesses through channels around component elements manually with the final connection being also accomplished manually thereby resulting in potential human error in the assembly. The potential for human error is reduced with the use of automated and in particular robotic assembly. However, robots are incapable or inefficient in handling wire harnesses due to the fact that the wires and cables vary in position due to their flexibility. In addition to the relatively high labor costs associated with harness construction and installation electrical wiring harnesses as well as their connectors are less than totally reliable in producing their intended function. Furthermore, and with increasing sophistication of the capabilities of such products, a plurality of wiring harnesses may be required in any individual machine which can require a large volume of space thereby increasing the overall size of the machine. Accordingly, there is a desire to provide an alternative to the conventional wiring and wiring harnesses that overcomes these difficulties.
Several techniques have been proposed to overcome these difficulties including techniques wherein three-dimensional features are molded into a chassis or casing with the potential to build circuitry into the chassis, subchassis or other part. Briefly, the aforementioned techniques can be categorized as utilizing dry processed or wet processes. Examples of dry techniques are the Konec process developed by Union Carbide and the Adap process developed by Allied Signal. Both processes involve a thermal transfer or embossment of either a conductive ink or metallic particles into the injection molded substrate. Another example of a dry process is the film-in-mold decorating technique where the film has a metalized pattern on it and is forced to conform to the interior of the mold and is bonded to the exterior of the molded part. While capable of use for simple circuitry patterns, they are limited in their abilities to produce fully three-dimensional conductive features. The wet processes can be described generally as semi-additive or fully additive with the latter being capable of providing selective metalization of planar and nonplanar three dimensional features on multiple surfaces of complex form. In the semiadditive processes, thermoplastic substrates are chemically pretreated to provide anchoring sites for subsequent catalyst absorption and metallization. Following the surface adhesion promotion treatment, the molded substrate is processes through a catalyst solution followed by electroless plating of a thin copper layer. Thereafter, resist application and image formation followed by copper electroplating and removal of the temporary resist are accomplished.
In addition, there are two fully additive techniques which permit selective plating on three-dimensional surfaces. In the Photoselective Plating process developed by PCK Technology Division of Kollomorgan Corporation, a photo imaginable plating catalyst is used to form three-dimensional images by selectively exposing catalyzed surfaces through a mask to ultraviolet light which initiates a photochemical reaction that converts the catalyst into metallic images corresponding to the desired circuit pattern. Thereafter, copper is applied to the circuit pattern in an electroless bath. The second additive technique is the Mold-n-Plate process also developed by PCK Technology Division wherein two different resin systems are used. One resin contains a plating additive while the second remains plating neutral. This involves a two-shot molding process wherein the first molding is with the resin containing the catalytic plating additive in a mold having the circuit design desired. This is followed by a second injection molding technique with the non-catalytic resin which covers areas of the molded part which are not part of the circuit and permits the circuit design to be exposed on the surface. Thereafter, copper plate is applied to the exposed circuit pattern made up of the resin containing the plating catalyst.
It has also been previously proposed (U.S. Pat. No. 4,286,250) to create electro-conductive pathways in electrically insulating polymers such as polyimides such as Kapton available from E. I. DuPont Company by exposing them to radiation from a laser to pyrolyze the polymer. While capable of providing a electro-conductive pathway, these pathways tend to be extremely delicate and subject to damage upon minimal handling. This is caused by the particulate nature of the conducting region that is only minimally adhered to the pathway resulting from the outgasing accompanying laser pyrolysis which disrupts the mechanical structure of the polymer.